1. Field of the Invention
The present invention relates to an apparatus for positioning a switch knob, and more specifically, to an apparatus for positioning a switch knob used for controlling on/off or the like of a battery feeded head lamp attached on a bicycle or the like.
2. Description of the Background Art
FIG. 7 is a side view showing a head lamp 101 employing a conventional positioning apparatus, attached on a handle 107 of a bicycle 143.
FIG. 8 shows a specific structure of the head lamp 101 attached on a handle 7 of FIG. 7, FIG. 9 is a front view and FIG. 10 is a rear view thereof.
Referring to these figures, an attachment part 102 consists of an upper member 109 and a lower member 111 which are rotatable around a pin 145. When attached to handle 107 of a bicycle, attachment screw 117 is removed, upper member 9 and lower member 111 are rotated about the pin 45 with their end portions expanded, and attachment part 102 is attached on the handle 107 of a bicycle with a rubber 47 wound around the handle 107. Thereafter, attachment screw 117 is fastened, so that a force gripping handle 107 is applied to the upper and lower members 109 and 111, and hence the attachment part 102 is firmly attached on handle 107 with rubber 147 interposed.
On a lamp body 125 at a rear portion of head lamp 101, a switch knob 103 for controlling on/off of the lamp is provided, which is operated referring to an indication mark 105. An attachment part 113 is attached on a lower portion of head lamp 101 by means of an attachment screw or the like. At a rear portion of attachment part 113, a lever 115 used for attachment/detachment to and from the attachment part 102 is provided.
FIG. 11 is a perspective view of switch knob 103 of FIG. 10 separated from lamp body 125 and a portion of the lamp body 125 viewed from the inside of the head lamp 101.
Referring to the figure, there is a rectangular opening 119 in lamp body 125. Opening 119 has opposing sidewalls 160a and 160b, the sidewall 160a is provided with two vertical grooves 161a and the sidewall 160b is provided with two vertical grooves 161b, which grooves each has semi-circular cross section and extending in thickness direction of the plate of the lamp body 125. At the opening 119 on the side of the lamp body 125, a switch plate 149 having a bent portion, and a terminal plate 151 positioned above a tip end of switch plate 149 are provided. When a switch plate 149 is brought into contact with terminal plate 151, a drive battery contained in head lamp 101 is electrically connected to the lamp, and the lamp is turned on.
Meanwhile, on the inner surface of a knob body 127 of switch knob 103, a pair of first projecting pieces 153a, 153b and a pair of second projecting pieces 157a and 157b are attached. The space between the first projecting piece 153a and the second projecting piece 157b, and the distance between the first projecting piece 53b and the second projecting piece 157a correspond to the space between opposing sidewalls 160a and 160b of the opening 119.
On the outer surfaces of the first projecting pieces 153a and 153b, semi-spherical projections 155a (not shown) and 155b are provided respectively. Near the tip ends of the second projecting pieces 157a and 157b, guide portions 137a and 137b having a triangular cross section are formed in a direction parallel to the upper surface of the knob body 127. At a central portion of the knob body 127, a third projecting piece 159 facing toward the switch plate 149 is attached.
FIG. 12 is a perspective view showing the switch knob 103 fitted in the opening 119, from the state of FIG. 11.
Referring to the figure, guide portions 137a and 137b formed at the second projecting pieces 157a and 157b respectively are engaged with the inner surface of lamp body 125 at the edges of opening 119, and guide sliding operation of switch knob 103 in the direction of the arrow. Projections 155a and 155b formed at the first projecting pieces 153a and 153b, respectively, engage with one of the vertical grooves 161a and one of the vertical grooves 161b, respectively. In the figure, switch knob 103 is positioned corresponding to a power off state. When the switch knob 103 slides in the direction of the arrow from this state, each of the projections 155a and 155b move to and engage with vertical grooves which are next to the vertical grooves with which the projections have been engaged, and the position of the switch knob 103 is stabilized. As the switch knob 103 is moved, the third projecting piece 159 projecting from the central portion of knob body 127 to the direction of the switch plate 149 also moves in the direction of the arrow, pushes up the tip end of switch plate 149, so that the tip end is brought into contact with the terminal plate 151. Therefore, the power is turned on and light is emitted from the head lamp 101.
In the conventional apparatus for positioning the switch knob as described above, it is difficult to have appropriate response of clicking when the knob is slid, since projections 155a and 155b engaging with vertical grooves 161a and 161b are attached on plate shaped projecting pieces 153a and 153b which pieces each have one end fixed on the knob body 127 and appropriate engaging force cannot be generated as the position of the projections must be on the side of the knob body 127. If the projections 155a and 155b are to be provided at tip ends of the first projecting pieces 153a and 153b, thickness of the first projecting pieces 153a and 153b must be increased. Further, since the first projecting pieces 153a and 153b have plate shape, they cannot be formed accurately by resin molding.
Therefore, projections 155a and 155b cannot be fitted with high precision in the vertical grooves 161a and 161b, and the projections cannot apply appropriate pressing force. As a result, good response of clicking cannot be obtained by the positioning apparatus.